Hendrik/xgboost
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
xgboost/src/tree/updater_gpu_hist.cu
Rory Mitchell 1be09848a7
Refactor split valuation kernel (#8073)
2022-07-21 15:41:50 +02:00

883 lines
34 KiB
Plaintext
Raw Blame History

/*!
* Copyright 2017-2022 XGBoost contributors
*/
#include <thrust/copy.h>
#include <thrust/reduce.h>
#include <xgboost/tree_updater.h>
#include <algorithm>
#include <cmath>
#include <memory>
#include <limits>
#include <utility>
#include <vector>
#include "xgboost/base.h"
#include "xgboost/data.h"
#include "xgboost/generic_parameters.h"
#include "xgboost/host_device_vector.h"
#include "xgboost/parameter.h"
#include "xgboost/span.h"
#include "xgboost/json.h"
#include "../common/io.h"
#include "../common/device_helpers.cuh"
#include "../common/hist_util.h"
#include "../common/bitfield.h"
#include "../common/timer.h"
#include "../common/categorical.h"
#include "../data/ellpack_page.cuh"
#include "param.h"
#include "driver.h"
#include "updater_gpu_common.cuh"
#include "split_evaluator.h"
#include "constraints.cuh"
#include "gpu_hist/feature_groups.cuh"
#include "gpu_hist/gradient_based_sampler.cuh"
#include "gpu_hist/row_partitioner.cuh"
#include "gpu_hist/histogram.cuh"
#include "gpu_hist/evaluate_splits.cuh"
#include "gpu_hist/expand_entry.cuh"
#include "xgboost/task.h"
#include "xgboost/tree_model.h"
namespace xgboost {
namespace tree {
#if !defined(GTEST_TEST)
DMLC_REGISTRY_FILE_TAG(updater_gpu_hist);
#endif // !defined(GTEST_TEST)
// training parameters specific to this algorithm
struct GPUHistMakerTrainParam
: public XGBoostParameter<GPUHistMakerTrainParam> {
bool debug_synchronize;
// declare parameters
DMLC_DECLARE_PARAMETER(GPUHistMakerTrainParam) {
DMLC_DECLARE_FIELD(debug_synchronize).set_default(false).describe(
"Check if all distributed tree are identical after tree construction.");
}
};
#if !defined(GTEST_TEST)
DMLC_REGISTER_PARAMETER(GPUHistMakerTrainParam);
#endif // !defined(GTEST_TEST)
/**
* \struct DeviceHistogramStorage
*
* \summary Data storage for node histograms on device. Automatically expands.
*
* \tparam GradientSumT histogram entry type.
* \tparam kStopGrowingSize Do not grow beyond this size
*
* \author Rory
* \date 28/07/2018
*/
template <typename GradientSumT, size_t kStopGrowingSize = 1 << 28>
class DeviceHistogramStorage {
private:
/*! \brief Map nidx to starting index of its histogram. */
std::map<int, size_t> nidx_map_;
// Large buffer of zeroed memory, caches histograms
dh::device_vector<typename GradientSumT::ValueT> data_;
// If we run out of storage allocate one histogram at a time
// in overflow. Not cached, overwritten when a new histogram
// is requested
dh::device_vector<typename GradientSumT::ValueT> overflow_;
std::map<int, size_t> overflow_nidx_map_;
int n_bins_;
int device_id_;
static constexpr size_t kNumItemsInGradientSum =
sizeof(GradientSumT) / sizeof(typename GradientSumT::ValueT);
static_assert(kNumItemsInGradientSum == 2, "Number of items in gradient type should be 2.");
public:
// Start with about 16mb
DeviceHistogramStorage() { data_.reserve(1 << 22); }
void Init(int device_id, int n_bins) {
this->n_bins_ = n_bins;
this->device_id_ = device_id;
}
void Reset() {
auto d_data = data_.data().get();
dh::LaunchN(data_.size(), [=] __device__(size_t idx) { d_data[idx] = 0.0f; });
nidx_map_.clear();
overflow_nidx_map_.clear();
}
bool HistogramExists(int nidx) const {
return nidx_map_.find(nidx) != nidx_map_.cend() ||
overflow_nidx_map_.find(nidx) != overflow_nidx_map_.cend();
}
int Bins() const { return n_bins_; }
size_t HistogramSize() const { return n_bins_ * kNumItemsInGradientSum; }
dh::device_vector<typename GradientSumT::ValueT>& Data() { return data_; }
void AllocateHistograms(const std::vector<int>& new_nidxs) {
for (int nidx : new_nidxs) {
CHECK(!HistogramExists(nidx));
}
// Number of items currently used in data
const size_t used_size = nidx_map_.size() * HistogramSize();
const size_t new_used_size = used_size + HistogramSize() * new_nidxs.size();
if (used_size >= kStopGrowingSize) {
// Use overflow
// Delete previous entries
overflow_nidx_map_.clear();
overflow_.resize(HistogramSize() * new_nidxs.size());
// Zero memory
auto d_data = overflow_.data().get();
dh::LaunchN(overflow_.size(),
[=] __device__(size_t idx) { d_data[idx] = 0.0; });
// Append new histograms
for (int nidx : new_nidxs) {
overflow_nidx_map_[nidx] = overflow_nidx_map_.size() * HistogramSize();
}
} else {
CHECK_GE(data_.size(), used_size);
// Expand if necessary
if (data_.size() < new_used_size) {
data_.resize(std::max(data_.size() * 2, new_used_size));
}
// Append new histograms
for (int nidx : new_nidxs) {
nidx_map_[nidx] = nidx_map_.size() * HistogramSize();
}
}
CHECK_GE(data_.size(), nidx_map_.size() * HistogramSize());
}
/**
* \summary Return pointer to histogram memory for a given node.
* \param nidx Tree node index.
* \return hist pointer.
*/
common::Span<GradientSumT> GetNodeHistogram(int nidx) {
CHECK(this->HistogramExists(nidx));
if (nidx_map_.find(nidx) != nidx_map_.cend()) {
// Fetch from normal cache
auto ptr = data_.data().get() + nidx_map_.at(nidx);
return common::Span<GradientSumT>(reinterpret_cast<GradientSumT*>(ptr), n_bins_);
} else {
// Fetch from overflow
auto ptr = overflow_.data().get() + overflow_nidx_map_.at(nidx);
return common::Span<GradientSumT>(reinterpret_cast<GradientSumT*>(ptr), n_bins_);
}
}
};
// Manage memory for a single GPU
template <typename GradientSumT>
struct GPUHistMakerDevice {
private:
GPUHistEvaluator evaluator_;
Context const* ctx_;
public:
EllpackPageImpl const* page;
common::Span<FeatureType const> feature_types;
BatchParam batch_param;
std::unique_ptr<RowPartitioner> row_partitioner;
DeviceHistogramStorage<GradientSumT> hist{};
dh::device_vector<GradientPair> d_gpair; // storage for gpair;
common::Span<GradientPair> gpair;
dh::device_vector<int> monotone_constraints;
dh::device_vector<float> update_predictions;
/*! \brief Sum gradient for each node. */
std::vector<GradientPairPrecise> node_sum_gradients;
TrainParam param;
HistRounding<GradientSumT> histogram_rounding;
dh::PinnedMemory pinned;
dh::PinnedMemory pinned2;
common::Monitor monitor;
common::ColumnSampler column_sampler;
FeatureInteractionConstraintDevice interaction_constraints;
std::unique_ptr<GradientBasedSampler> sampler;
std::unique_ptr<FeatureGroups> feature_groups;
GPUHistMakerDevice(Context const* ctx, EllpackPageImpl const* _page,
common::Span<FeatureType const> _feature_types, bst_uint _n_rows,
TrainParam _param, uint32_t column_sampler_seed, uint32_t n_features,
BatchParam _batch_param)
: evaluator_{_param, n_features, ctx->gpu_id},
ctx_(ctx),
page(_page),
feature_types{_feature_types},
param(std::move(_param)),
column_sampler(column_sampler_seed),
interaction_constraints(param, n_features),
batch_param(std::move(_batch_param)) {
sampler.reset(new GradientBasedSampler(page, _n_rows, batch_param, param.subsample,
param.sampling_method));
if (!param.monotone_constraints.empty()) {
// Copy assigning an empty vector causes an exception in MSVC debug builds
monotone_constraints = param.monotone_constraints;
}
node_sum_gradients.resize(256);
// Init histogram
hist.Init(ctx_->gpu_id, page->Cuts().TotalBins());
monitor.Init(std::string("GPUHistMakerDevice") + std::to_string(ctx_->gpu_id));
feature_groups.reset(new FeatureGroups(page->Cuts(), page->is_dense,
dh::MaxSharedMemoryOptin(ctx_->gpu_id),
sizeof(GradientSumT)));
}
~GPUHistMakerDevice() { // NOLINT
dh::safe_cuda(cudaSetDevice(ctx_->gpu_id));
}
// Reset values for each update iteration
// Note that the column sampler must be passed by value because it is not
// thread safe
void Reset(HostDeviceVector<GradientPair>* dh_gpair, DMatrix* dmat, int64_t num_columns) {
auto const& info = dmat->Info();
this->column_sampler.Init(num_columns, info.feature_weights.HostVector(),
param.colsample_bynode, param.colsample_bylevel,
param.colsample_bytree);
dh::safe_cuda(cudaSetDevice(ctx_->gpu_id));
this->evaluator_.Reset(page->Cuts(), feature_types, dmat->Info().num_col_, param,
ctx_->gpu_id);
this->interaction_constraints.Reset();
std::fill(node_sum_gradients.begin(), node_sum_gradients.end(), GradientPairPrecise{});
if (d_gpair.size() != dh_gpair->Size()) {
d_gpair.resize(dh_gpair->Size());
}
dh::safe_cuda(cudaMemcpyAsync(
d_gpair.data().get(), dh_gpair->ConstDevicePointer(),
dh_gpair->Size() * sizeof(GradientPair), cudaMemcpyDeviceToDevice));
auto sample = sampler->Sample(dh::ToSpan(d_gpair), dmat);
page = sample.page;
gpair = sample.gpair;
histogram_rounding = CreateRoundingFactor<GradientSumT>(this->gpair);
row_partitioner.reset(); // Release the device memory first before reallocating
row_partitioner.reset(new RowPartitioner(ctx_->gpu_id, sample.sample_rows));
hist.Reset();
}
GPUExpandEntry EvaluateRootSplit(GradientPairPrecise root_sum) {
int nidx = RegTree::kRoot;
GPUTrainingParam gpu_param(param);
auto sampled_features = column_sampler.GetFeatureSet(0);
sampled_features->SetDevice(ctx_->gpu_id);
common::Span<bst_feature_t> feature_set =
interaction_constraints.Query(sampled_features->DeviceSpan(), nidx);
auto matrix = page->GetDeviceAccessor(ctx_->gpu_id);
EvaluateSplitInputs inputs{nidx, 0, root_sum, feature_set, hist.GetNodeHistogram(nidx)};
EvaluateSplitSharedInputs shared_inputs{
gpu_param, feature_types, matrix.feature_segments, matrix.gidx_fvalue_map,
matrix.min_fvalue,
};
auto split = this->evaluator_.EvaluateSingleSplit(inputs, shared_inputs);
return split;
}
void EvaluateSplits(const std::vector<GPUExpandEntry>& candidates, const RegTree& tree,
common::Span<GPUExpandEntry> pinned_candidates_out) {
if (candidates.empty()) return;
dh::TemporaryArray<EvaluateSplitInputs> d_node_inputs(2 * candidates.size());
dh::TemporaryArray<DeviceSplitCandidate> splits_out(2 * candidates.size());
std::vector<bst_node_t> nidx(2 * candidates.size());
auto h_node_inputs = pinned2.GetSpan<EvaluateSplitInputs>(2 * candidates.size());
auto matrix = page->GetDeviceAccessor(ctx_->gpu_id);
EvaluateSplitSharedInputs shared_inputs{
GPUTrainingParam{param}, feature_types, matrix.feature_segments,
matrix.gidx_fvalue_map, matrix.min_fvalue,
};
dh::TemporaryArray<GPUExpandEntry> entries(2 * candidates.size());
for (size_t i = 0; i < candidates.size(); i++) {
auto candidate = candidates.at(i);
int left_nidx = tree[candidate.nid].LeftChild();
int right_nidx = tree[candidate.nid].RightChild();
nidx[i * 2] = left_nidx;
nidx[i * 2 + 1] = right_nidx;
auto left_sampled_features = column_sampler.GetFeatureSet(tree.GetDepth(left_nidx));
left_sampled_features->SetDevice(ctx_->gpu_id);
common::Span<bst_feature_t> left_feature_set =
interaction_constraints.Query(left_sampled_features->DeviceSpan(), left_nidx);
auto right_sampled_features = column_sampler.GetFeatureSet(tree.GetDepth(right_nidx));
right_sampled_features->SetDevice(ctx_->gpu_id);
common::Span<bst_feature_t> right_feature_set =
interaction_constraints.Query(right_sampled_features->DeviceSpan(), left_nidx);
h_node_inputs[i * 2] = {left_nidx, candidate.depth + 1, candidate.split.left_sum,
left_feature_set, hist.GetNodeHistogram(left_nidx)};
h_node_inputs[i * 2 + 1] = {right_nidx, candidate.depth + 1, candidate.split.right_sum,
right_feature_set, hist.GetNodeHistogram(right_nidx)};
}
bst_feature_t number_active_features = h_node_inputs[0].feature_set.size();
for (auto input : h_node_inputs) {
CHECK_EQ(input.feature_set.size(), number_active_features)
<< "Current implementation assumes that the number of active features "
"(after sampling) in any node is the same";
}
dh::safe_cuda(cudaMemcpyAsync(d_node_inputs.data().get(), h_node_inputs.data(),
h_node_inputs.size() * sizeof(EvaluateSplitInputs),
cudaMemcpyDefault));
this->evaluator_.EvaluateSplits(nidx, number_active_features, dh::ToSpan(d_node_inputs),
shared_inputs, dh::ToSpan(entries));
dh::safe_cuda(cudaMemcpyAsync(pinned_candidates_out.data(),
entries.data().get(), sizeof(GPUExpandEntry) * entries.size(),
cudaMemcpyDeviceToHost));
dh::DefaultStream().Sync();
}
void BuildHist(int nidx) {
auto d_node_hist = hist.GetNodeHistogram(nidx);
auto d_ridx = row_partitioner->GetRows(nidx);
BuildGradientHistogram(page->GetDeviceAccessor(ctx_->gpu_id),
feature_groups->DeviceAccessor(ctx_->gpu_id), gpair,
d_ridx, d_node_hist, histogram_rounding);
}
// Attempt to do subtraction trick
// return true if succeeded
bool SubtractionTrick(int nidx_parent, int nidx_histogram, int nidx_subtraction) {
if (!hist.HistogramExists(nidx_histogram) || !hist.HistogramExists(nidx_parent)) {
return false;
}
auto d_node_hist_parent = hist.GetNodeHistogram(nidx_parent);
auto d_node_hist_histogram = hist.GetNodeHistogram(nidx_histogram);
auto d_node_hist_subtraction = hist.GetNodeHistogram(nidx_subtraction);
dh::LaunchN(page->Cuts().TotalBins(), [=] __device__(size_t idx) {
d_node_hist_subtraction[idx] =
d_node_hist_parent[idx] - d_node_hist_histogram[idx];
});
return true;
}
// Extra data for each node that is passed
// to the update position function
struct NodeSplitData {
RegTree::Node split_node;
FeatureType split_type;
common::CatBitField node_cats;
};
void UpdatePosition(const std::vector<GPUExpandEntry>& candidates, RegTree* p_tree) {
if (candidates.empty()) return;
std::vector<int> nidx(candidates.size());
std::vector<int> left_nidx(candidates.size());
std::vector<int> right_nidx(candidates.size());
std::vector<NodeSplitData> split_data(candidates.size());
for (size_t i = 0; i < candidates.size(); i++) {
auto& e = candidates[i];
RegTree::Node split_node = (*p_tree)[e.nid];
auto split_type = p_tree->NodeSplitType(e.nid);
nidx.at(i) = e.nid;
left_nidx.at(i) = split_node.LeftChild();
right_nidx.at(i) = split_node.RightChild();
split_data.at(i) = NodeSplitData{split_node, split_type, e.split.split_cats};
}
auto d_matrix = page->GetDeviceAccessor(ctx_->gpu_id);
row_partitioner->UpdatePositionBatch(
nidx, left_nidx, right_nidx, split_data,
[=] __device__(bst_uint ridx, const NodeSplitData& data) {
// given a row index, returns the node id it belongs to
bst_float cut_value = d_matrix.GetFvalue(ridx, data.split_node.SplitIndex());
// Missing value
bool go_left = true;
if (isnan(cut_value)) {
go_left = data.split_node.DefaultLeft();
} else {
if (data.split_type == FeatureType::kCategorical) {
go_left = common::Decision<false>(data.node_cats.Bits(), cut_value,
data.split_node.DefaultLeft());
} else {
go_left = cut_value <= data.split_node.SplitCond();
}
}
return go_left;
});
}
// After tree update is finished, update the position of all training
// instances to their final leaf. This information is used later to update the
// prediction cache
void FinalisePosition(RegTree const* p_tree, DMatrix* p_fmat, ObjInfo task,
HostDeviceVector<bst_node_t>* p_out_position) {
// Prediction cache will not be used with external memory
if (!p_fmat->SingleColBlock()) {
if (task.UpdateTreeLeaf()) {
LOG(FATAL) << "Current objective function can not be used with external memory.";
}
p_out_position->Resize(0);
update_predictions.clear();
return;
}
dh::TemporaryArray<RegTree::Node> d_nodes(p_tree->GetNodes().size());
dh::safe_cuda(cudaMemcpyAsync(d_nodes.data().get(), p_tree->GetNodes().data(),
d_nodes.size() * sizeof(RegTree::Node),
cudaMemcpyHostToDevice));
auto const& h_split_types = p_tree->GetSplitTypes();
auto const& categories = p_tree->GetSplitCategories();
auto const& categories_segments = p_tree->GetSplitCategoriesPtr();
dh::caching_device_vector<FeatureType> d_split_types;
dh::caching_device_vector<uint32_t> d_categories;
dh::caching_device_vector<RegTree::Segment> d_categories_segments;
if (!categories.empty()) {
dh::CopyToD(h_split_types, &d_split_types);
dh::CopyToD(categories, &d_categories);
dh::CopyToD(categories_segments, &d_categories_segments);
}
FinalisePositionInPage(page, dh::ToSpan(d_nodes), dh::ToSpan(d_split_types),
dh::ToSpan(d_categories), dh::ToSpan(d_categories_segments),
p_out_position);
}
void FinalisePositionInPage(EllpackPageImpl const *page,
const common::Span<RegTree::Node> d_nodes,
common::Span<FeatureType const> d_feature_types,
common::Span<uint32_t const> categories,
common::Span<RegTree::Segment> categories_segments,
HostDeviceVector<bst_node_t>* p_out_position) {
auto d_matrix = page->GetDeviceAccessor(ctx_->gpu_id);
auto d_gpair = this->gpair;
update_predictions.resize(row_partitioner->GetRows().size());
auto d_update_predictions = dh::ToSpan(update_predictions);
p_out_position->SetDevice(ctx_->gpu_id);
p_out_position->Resize(row_partitioner->GetRows().size());
auto new_position_op = [=] __device__(size_t row_id, int position) {
// What happens if user prune the tree?
if (!d_matrix.IsInRange(row_id)) {
return RowPartitioner::kIgnoredTreePosition;
}
auto node = d_nodes[position];
while (!node.IsLeaf()) {
bst_float element = d_matrix.GetFvalue(row_id, node.SplitIndex());
// Missing value
if (isnan(element)) {
position = node.DefaultChild();
} else {
bool go_left = true;
if (common::IsCat(d_feature_types, position)) {
auto node_cats = categories.subspan(categories_segments[position].beg,
categories_segments[position].size);
go_left = common::Decision<false>(node_cats, element, node.DefaultLeft());
} else {
go_left = element <= node.SplitCond();
}
if (go_left) {
position = node.LeftChild();
} else {
position = node.RightChild();
}
}
node = d_nodes[position];
}
d_update_predictions[row_id] = node.LeafValue();
return position;
}; // NOLINT
auto d_out_position = p_out_position->DeviceSpan();
row_partitioner->FinalisePosition(d_out_position, new_position_op);
dh::LaunchN(row_partitioner->GetRows().size(), [=] __device__(size_t idx) {
bst_node_t position = d_out_position[idx];
d_update_predictions[idx] = d_nodes[position].LeafValue();
bool is_row_sampled = d_gpair[idx].GetHess() - .0f == 0.f;
d_out_position[idx] = is_row_sampled ? ~position : position;
});
}
bool UpdatePredictionCache(linalg::VectorView<float> out_preds_d, RegTree const* p_tree) {
if (update_predictions.empty()) {
return false;
}
CHECK(p_tree);
dh::safe_cuda(cudaSetDevice(ctx_->gpu_id));
CHECK_EQ(out_preds_d.DeviceIdx(), ctx_->gpu_id);
auto d_update_predictions = dh::ToSpan(update_predictions);
CHECK_EQ(out_preds_d.Size(), d_update_predictions.size());
dh::LaunchN(out_preds_d.Size(), [=] XGBOOST_DEVICE(size_t idx) mutable {
out_preds_d(idx) += d_update_predictions[idx];
});
return true;
}
// num histograms is the number of contiguous histograms in memory to reduce over
void AllReduceHist(int nidx, dh::AllReducer* reducer, int num_histograms) {
monitor.Start("AllReduce");
auto d_node_hist = hist.GetNodeHistogram(nidx).data();
reducer->AllReduceSum(reinterpret_cast<typename GradientSumT::ValueT*>(d_node_hist),
reinterpret_cast<typename GradientSumT::ValueT*>(d_node_hist),
page->Cuts().TotalBins() *
(sizeof(GradientSumT) / sizeof(typename GradientSumT::ValueT)) *
num_histograms);
monitor.Stop("AllReduce");
}
/**
* \brief Build GPU local histograms for the left and right child of some parent node
*/
void BuildHistLeftRight(std::vector<GPUExpandEntry> const& candidates, dh::AllReducer* reducer,
const RegTree& tree) {
if (candidates.empty()) return;
// Some nodes we will manually compute histograms
// others we will do by subtraction
std::vector<int> hist_nidx;
std::vector<int> subtraction_nidx;
for (auto& e : candidates) {
// Decide whether to build the left histogram or right histogram
// Use sum of Hessian as a heuristic to select node with fewest training instances
bool fewer_right = e.split.right_sum.GetHess() < e.split.left_sum.GetHess();
if (fewer_right) {
hist_nidx.emplace_back(tree[e.nid].RightChild());
subtraction_nidx.emplace_back(tree[e.nid].LeftChild());
} else {
hist_nidx.emplace_back(tree[e.nid].LeftChild());
subtraction_nidx.emplace_back(tree[e.nid].RightChild());
}
}
std::vector<int> all_new = hist_nidx;
all_new.insert(all_new.end(), subtraction_nidx.begin(), subtraction_nidx.end());
// Allocate the histograms
// Guaranteed contiguous memory
hist.AllocateHistograms(all_new);
for (auto nidx : hist_nidx) {
this->BuildHist(nidx);
}
// Reduce all in one go
// This gives much better latency in a distributed setting
// when processing a large batch
this->AllReduceHist(hist_nidx.at(0), reducer, hist_nidx.size());
for (size_t i = 0; i < subtraction_nidx.size(); i++) {
auto build_hist_nidx = hist_nidx.at(i);
auto subtraction_trick_nidx = subtraction_nidx.at(i);
auto parent_nidx = candidates.at(i).nid;
if (!this->SubtractionTrick(parent_nidx, build_hist_nidx, subtraction_trick_nidx)) {
// Calculate other histogram manually
this->BuildHist(subtraction_trick_nidx);
this->AllReduceHist(subtraction_trick_nidx, reducer, 1);
}
}
}
void ApplySplit(const GPUExpandEntry& candidate, RegTree* p_tree) {
RegTree& tree = *p_tree;
// Sanity check - have we created a leaf with no training instances?
if (!rabit::IsDistributed() && row_partitioner) {
CHECK(row_partitioner->GetRows(candidate.nid).size() > 0)
<< "No training instances in this leaf!";
}
auto parent_sum = candidate.split.left_sum + candidate.split.right_sum;
auto base_weight = candidate.base_weight;
auto left_weight = candidate.left_weight * param.learning_rate;
auto right_weight = candidate.right_weight * param.learning_rate;
auto is_cat = candidate.split.is_cat;
if (is_cat) {
CHECK_LT(candidate.split.fvalue, std::numeric_limits<bst_cat_t>::max())
<< "Categorical feature value too large.";
std::vector<uint32_t> split_cats;
CHECK_GT(candidate.split.split_cats.Bits().size(), 0);
auto h_cats = this->evaluator_.GetHostNodeCats(candidate.nid);
auto max_cat = candidate.split.MaxCat();
split_cats.resize(common::CatBitField::ComputeStorageSize(max_cat + 1), 0);
CHECK_LE(split_cats.size(), h_cats.size());
std::copy(h_cats.data(), h_cats.data() + split_cats.size(), split_cats.data());
tree.ExpandCategorical(
candidate.nid, candidate.split.findex, split_cats, candidate.split.dir == kLeftDir,
base_weight, left_weight, right_weight, candidate.split.loss_chg, parent_sum.GetHess(),
candidate.split.left_sum.GetHess(), candidate.split.right_sum.GetHess());
} else {
tree.ExpandNode(candidate.nid, candidate.split.findex, candidate.split.fvalue,
candidate.split.dir == kLeftDir, base_weight, left_weight, right_weight,
candidate.split.loss_chg, parent_sum.GetHess(),
candidate.split.left_sum.GetHess(), candidate.split.right_sum.GetHess());
}
evaluator_.ApplyTreeSplit(candidate, p_tree);
const auto& parent = tree[candidate.nid];
std::size_t max_nidx = std::max(parent.LeftChild(), parent.RightChild());
// Grow as needed
if (node_sum_gradients.size() <= max_nidx) {
node_sum_gradients.resize(max_nidx * 2 + 1);
}
node_sum_gradients[parent.LeftChild()] = candidate.split.left_sum;
node_sum_gradients[parent.RightChild()] = candidate.split.right_sum;
interaction_constraints.Split(candidate.nid, parent.SplitIndex(), parent.LeftChild(),
parent.RightChild());
}
GPUExpandEntry InitRoot(RegTree* p_tree, dh::AllReducer* reducer) {
constexpr bst_node_t kRootNIdx = 0;
dh::XGBCachingDeviceAllocator<char> alloc;
auto gpair_it = dh::MakeTransformIterator<GradientPairPrecise>(
dh::tbegin(gpair), [] __device__(auto const& gpair) { return GradientPairPrecise{gpair}; });
GradientPairPrecise root_sum =
dh::Reduce(thrust::cuda::par(alloc), gpair_it, gpair_it + gpair.size(),
GradientPairPrecise{}, thrust::plus<GradientPairPrecise>{});
rabit::Allreduce<rabit::op::Sum, double>(reinterpret_cast<double*>(&root_sum), 2);
hist.AllocateHistograms({kRootNIdx});
this->BuildHist(kRootNIdx);
this->AllReduceHist(kRootNIdx, reducer, 1);
// Remember root stats
node_sum_gradients[kRootNIdx] = root_sum;
p_tree->Stat(kRootNIdx).sum_hess = root_sum.GetHess();
auto weight = CalcWeight(param, root_sum);
p_tree->Stat(kRootNIdx).base_weight = weight;
(*p_tree)[kRootNIdx].SetLeaf(param.learning_rate * weight);
// Generate first split
auto root_entry = this->EvaluateRootSplit(root_sum);
return root_entry;
}
void UpdateTree(HostDeviceVector<GradientPair>* gpair_all, DMatrix* p_fmat, ObjInfo task,
RegTree* p_tree, dh::AllReducer* reducer,
HostDeviceVector<bst_node_t>* p_out_position) {
auto& tree = *p_tree;
// Process maximum 32 nodes at a time
Driver<GPUExpandEntry> driver(param, 32);
monitor.Start("Reset");
this->Reset(gpair_all, p_fmat, p_fmat->Info().num_col_);
monitor.Stop("Reset");
monitor.Start("InitRoot");
driver.Push({ this->InitRoot(p_tree, reducer) });
monitor.Stop("InitRoot");
// The set of leaves that can be expanded asynchronously
auto expand_set = driver.Pop();
while (!expand_set.empty()) {
for (auto& candidate : expand_set) {
this->ApplySplit(candidate, p_tree);
}
// Get the candidates we are allowed to expand further
// e.g. We do not bother further processing nodes whose children are beyond max depth
std::vector<GPUExpandEntry> filtered_expand_set;
std::copy_if(expand_set.begin(), expand_set.end(), std::back_inserter(filtered_expand_set),
[&](const auto& e) { return driver.IsChildValid(e); });
auto new_candidates =
pinned.GetSpan<GPUExpandEntry>(filtered_expand_set.size() * 2, GPUExpandEntry());
monitor.Start("UpdatePosition");
// Update position is only run when child is valid, instead of right after apply
// split (as in approx tree method). Hense we have the finalise position call
// in GPU Hist.
this->UpdatePosition(filtered_expand_set, p_tree);
monitor.Stop("UpdatePosition");
monitor.Start("BuildHist");
this->BuildHistLeftRight(filtered_expand_set, reducer, tree);
monitor.Stop("BuildHist");
monitor.Start("EvaluateSplits");
this->EvaluateSplits(filtered_expand_set, *p_tree, new_candidates);
monitor.Stop("EvaluateSplits");
dh::DefaultStream().Sync();
driver.Push(new_candidates.begin(), new_candidates.end());
expand_set = driver.Pop();
}
monitor.Start("FinalisePosition");
this->FinalisePosition(p_tree, p_fmat, task, p_out_position);
monitor.Stop("FinalisePosition");
}
};
class GPUHistMaker : public TreeUpdater {
using GradientSumT = GradientPairPrecise;
public:
explicit GPUHistMaker(GenericParameter const* ctx, ObjInfo task)
: TreeUpdater(ctx), task_{task} {};
void Configure(const Args& args) override {
// Used in test to count how many configurations are performed
LOG(DEBUG) << "[GPU Hist]: Configure";
param_.UpdateAllowUnknown(args);
hist_maker_param_.UpdateAllowUnknown(args);
dh::CheckComputeCapability();
initialised_ = false;
monitor_.Init("updater_gpu_hist");
}
void LoadConfig(Json const& in) override {
auto const& config = get<Object const>(in);
FromJson(config.at("gpu_hist_train_param"), &this->hist_maker_param_);
initialised_ = false;
FromJson(config.at("train_param"), &param_);
}
void SaveConfig(Json* p_out) const override {
auto& out = *p_out;
out["gpu_hist_train_param"] = ToJson(hist_maker_param_);
out["train_param"] = ToJson(param_);
}
~GPUHistMaker() { // NOLINT
dh::GlobalMemoryLogger().Log();
}
void Update(HostDeviceVector<GradientPair>* gpair, DMatrix* dmat,
common::Span<HostDeviceVector<bst_node_t>> out_position,
const std::vector<RegTree*>& trees) override {
monitor_.Start("Update");
// rescale learning rate according to size of trees
float lr = param_.learning_rate;
param_.learning_rate = lr / trees.size();
// build tree
try {
size_t t_idx{0};
for (xgboost::RegTree* tree : trees) {
this->UpdateTree(gpair, dmat, tree, &out_position[t_idx]);
if (hist_maker_param_.debug_synchronize) {
this->CheckTreesSynchronized(tree);
}
++t_idx;
}
dh::safe_cuda(cudaGetLastError());
} catch (const std::exception& e) {
LOG(FATAL) << "Exception in gpu_hist: " << e.what() << std::endl;
}
param_.learning_rate = lr;
monitor_.Stop("Update");
}
void InitDataOnce(DMatrix* dmat) {
CHECK_GE(ctx_->gpu_id, 0) << "Must have at least one device";
info_ = &dmat->Info();
reducer_.Init({ctx_->gpu_id}); // NOLINT
// Synchronise the column sampling seed
uint32_t column_sampling_seed = common::GlobalRandom()();
rabit::Broadcast(&column_sampling_seed, sizeof(column_sampling_seed), 0);
BatchParam batch_param{
ctx_->gpu_id,
param_.max_bin,
};
auto page = (*dmat->GetBatches<EllpackPage>(batch_param).begin()).Impl();
dh::safe_cuda(cudaSetDevice(ctx_->gpu_id));
info_->feature_types.SetDevice(ctx_->gpu_id);
maker.reset(new GPUHistMakerDevice<GradientSumT>(
ctx_, page, info_->feature_types.ConstDeviceSpan(), info_->num_row_, param_,
column_sampling_seed, info_->num_col_, batch_param));
p_last_fmat_ = dmat;
initialised_ = true;
}
void InitData(DMatrix* dmat, RegTree const* p_tree) {
if (!initialised_) {
monitor_.Start("InitDataOnce");
this->InitDataOnce(dmat);
monitor_.Stop("InitDataOnce");
}
p_last_tree_ = p_tree;
}
// Only call this method for testing
void CheckTreesSynchronized(RegTree* local_tree) const {
std::string s_model;
common::MemoryBufferStream fs(&s_model);
int rank = rabit::GetRank();
if (rank == 0) {
local_tree->Save(&fs);
}
fs.Seek(0);
rabit::Broadcast(&s_model, 0);
RegTree reference_tree{}; // rank 0 tree
reference_tree.Load(&fs);
CHECK(*local_tree == reference_tree);
}
void UpdateTree(HostDeviceVector<GradientPair>* gpair, DMatrix* p_fmat, RegTree* p_tree,
HostDeviceVector<bst_node_t>* p_out_position) {
monitor_.Start("InitData");
this->InitData(p_fmat, p_tree);
monitor_.Stop("InitData");
gpair->SetDevice(ctx_->gpu_id);
maker->UpdateTree(gpair, p_fmat, task_, p_tree, &reducer_, p_out_position);
}
bool UpdatePredictionCache(const DMatrix* data,
linalg::VectorView<bst_float> p_out_preds) override {
if (maker == nullptr || p_last_fmat_ == nullptr || p_last_fmat_ != data) {
return false;
}
monitor_.Start("UpdatePredictionCache");
bool result = maker->UpdatePredictionCache(p_out_preds, p_last_tree_);
monitor_.Stop("UpdatePredictionCache");
return result;
}
TrainParam param_; // NOLINT
MetaInfo* info_{}; // NOLINT
std::unique_ptr<GPUHistMakerDevice<GradientSumT>> maker; // NOLINT
char const* Name() const override { return "grow_gpu_hist"; }
private:
bool initialised_{false};
GPUHistMakerTrainParam hist_maker_param_;
dh::AllReducer reducer_;
DMatrix* p_last_fmat_{nullptr};
RegTree const* p_last_tree_{nullptr};
ObjInfo task_;
common::Monitor monitor_;
};
#if !defined(GTEST_TEST)
XGBOOST_REGISTER_TREE_UPDATER(GPUHistMaker, "grow_gpu_hist")
.describe("Grow tree with GPU.")
.set_body([](GenericParameter const* tparam, ObjInfo task) {
return new GPUHistMaker(tparam, task);
});
#endif // !defined(GTEST_TEST)
} // namespace tree
} // namespace xgboost
Reference in New Issue View Git Blame Copy Permalink